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Abstract:

An antenna system comprising a ground plane, an antenna element folded
under itself and operable to transmit and receive circularly polarized
signals, an air filled cavity disposed between the ground plane and the
antenna element, and a radio frequency module in communication with the
antenna element.

Claims:

1. An antenna element formed from a conductor that is shaped to provide a
first layer, a wall layer, and a second layer, wherein the second layer
comprises a plurality of arms under the first layer, and wherein
asymmetries are present in the antenna element so that the antenna
element is configured to generate and receive circularly polarized
signals.

2. The antenna element of claim 1 wherein the conductive element includes
a plurality of slots that create meandering radiation paths.

3. The antenna element of claim 2 wherein the asymmetries are in the first
layer.

4. The antenna element of claim 2 wherein the asymmetries are in the
second layer.

5. The antenna element of claim 2 wherein the asymmetries are in the wall
layer.

6. The antenna element of claim 1 wherein the wall layer comprises walls
of different heights.

7. The antenna element of claim 1 wherein the wall layer is constructed of
items selected from the list consisting of:a portion of a conductive
layer that also forms the first layer; andone or more conductive pins.

8. The antenna element of claim 1 wherein the conductive element is
further shaped to provide a second wall layer and a third layer under the
second layer.

9. A miniature folded patch antenna comprising:an antenna element formed
from a conductor that is shaped to provide a first layer, a wall layer,
and a second layer, wherein the second layer comprises a plurality of
arms under the first layer, and wherein asymmetries are present in the
antenna element so that the antenna element is configured to generate and
receive circularly polarized signals;a ground plane separated from the
antenna element by a spacer layer; anda feed element between the antenna
element and the ground plane.

11. The miniature folded patch antenna of claim 9 wherein the miniature
folded patch antenna is a component in a mobile communications device.

12. An antenna element comprising:a conductive patch formed on a first
printed circuit board;a series of conductive patches on a second printed
circuit board, wherein the conductive patch on the first printed circuit
board is coupled to the series of conductive patches on the second
printed circuit board by a plurality of conducting pins; andwherein an
asymmetry is present in the antenna element configuring the antenna
element to transmit and receive circularly polarized signals.

13. The antenna element of claim 12 wherein the asymmetry is present in
the conductive patch formed on the first printed circuit board.

14. The antenna element of claim 12 wherein the asymmetry is present in
the series of conductive patches on the second printed circuit board.

15. The antenna element of claim 12 wherein the first printed circuit
board and the second printed circuit board are separated by a layer of
air.

16. The antenna element of claim 12 wherein the first printed circuit
board and the second printed circuit board are separated by a dielectric
material.

17. A patch antenna comprising:a conductive patch formed on a first
printed circuit board;a series of conductive patches on a second printed
circuit board, wherein the conductive patch on the first printed circuit
board is coupled to the series of conductive patches on the second
printed circuit board by a plurality of conducting pins, wherein an
asymmetry is present in the series of conductive patches configuring the
antenna element to transmit and receive circularly polarized signals;a
ground plane separated from the antenna element by a spacer layer; anda
radio frequency module in communication with the antenna element and
transmitting and receiving radio waves through the first antenna element.

18. The patch antenna of claim 17 wherein the spacer layer comprises an
air gap.

19. The patch antenna of claim 17 wherein the spacer layer includes a
dielectric.

20. An antenna element formed from a single conductor that is shaped to
provide a first layer, a wall layer, and a second layer, wherein the
second layer comprises a plurality of arms folded under the first layer,
and wherein asymmetries are present in the antenna element so that the
antenna element is configured to generate and receive circularly
polarized signals.

21. The antenna element of claim 20 wherein the conductive element
includes a plurality of slots that create meandering radiation paths.

22. The antenna element of claim 20 wherein the antenna element is further
shaped to provide a second wall layer and a third layer under the second
layer.

23. The antenna element of claim 22 wherein the asymmetries are in the
third layer.

24. A method of making a radiating element for a patch antenna
comprising:providing a flat conductor;forming an antenna element from the
flat conductor, wherein a pattern of the antenna element includes a
plurality of slots and asymmetries that cause a signal fed to the antenna
element to degenerate into two modes; andmanipulating the antenna element
about a first set of generally parallel fold lines so as to form a top
layer, a wall layer, and a bottom layer.

25. The method of claim 24 wherein the asymmetries are in the top layer.

26. The method of claim 24 wherein the asymmetries are in the bottom
layer.

27. The method of claim 24 wherein the asymmetries are in the wall layer.

28. The method of claim 24 further comprising: tuning the antenna element
by electrically connecting portions of the pattern.

[0002]A large number of radio applications, including satellite
communication, global positioning system (GPS), and radio frequency
identification (RFID) base stations, utilize circularly polarized
signals. Circular polarization (CP) of electromagnetic radiation is a
polarization such that the electric field of the radiation varies in two
orthogonal planes (the major and minor axis) with the same magnitude.
Perfect CP is where the major and minor components are of equal magnitude
and 90° out of phase. Most real world CP signals are not perfectly
circular; rather, the signals are elliptical. That is, the orthogonal
components are not of equal amplitude or not strictly 90° out of
phase. The quality of circular polarization is quantified as the axial
ratio. Axial ratio is defined as the voltage ratio of the major axis to
the minor axis of the polarization ellipse and is expressed in decibels
(dB). An axial ratio of less than 3 dB is considered sufficient for most
CP applications. For a good circularly polarized antenna design, axial
ratio bandwidth (the frequency band having axial ratio below 3 dB) is
necessarily ranged inside the impedance bandwidth. This ensures that the
received or transmitted CP signal of the antenna has maximum power
transfer.

[0003]Microstrip or patch antennas are increasingly used in GPS, satellite
communications, personal communication systems, and other communication
systems that utilize circularly polarized signals. A patch antenna is a
resonator-type antenna that generally includes an electrically conductive
ground layer, an electrically conductive patch antenna element, a feeding
geometry, and a dielectric substrate or an air filled cavity disposed
between the ground layer and conductive patch antenna element. There are
two primary approaches to accomplish circular polarization in patch
antennas.

[0004]One approach is to excite a single patch with two feeds, with one
feed delayed by 90° with respect to the other. This drives two
transverse modes with equal amplitudes and 90° out of phase. Each
mode radiates separately, and the modes combine to produce circular
polarization. A second approach is to use a single feed but introduce an
asymmetry into the patch, causing current distribution to be displaced.
The resonance frequencies of the two paths can be adjusted so that the
phase difference between the two paths is 90°. Thus circular
polarization can be achieved by building a patch with two resonance
frequencies in orthogonal directions.

[0005]Prior art CP patch antennas are typically in the range of half a
wavelength in length. Prior art patch antennas utilize several different
technologies to enable miniaturization (length<0.2λ0). The
most common solution is dielectric loading with high dielectric constant
material, but there are several drawbacks with this method.
Dielectrically loaded patch antennas often exhibit narrow bandwidth, high
loss, and poor efficiency. Moreover, dielectrically loaded patch antennas
are often expensive, heavy, and difficult to manufacture.

BRIEF SUMMARY OF THE INVENTION

[0006]Various embodiments of the invention are directed to antenna systems
that include a ground plane, an antenna element folded under itself and
with asymmetries that allow the antenna element to generate and receive
circularly polarized signals, an air filled cavity disposed between the
ground plane and the antenna element, and a radio frequency module in
communication with the antenna element and transmitting and receiving
radio waves through the antenna element.

[0007]The foregoing has outlined rather broadly the features and technical
advantages of the present invention in order that the detailed
description of the invention that follows may be better understood.
Additional features and advantages of the invention will be described
hereinafter which form the subject of the claims of the invention. It
should be appreciated by those skilled in the art that the conception and
specific embodiment disclosed may be readily utilized as a basis for
modifying or designing other structures for carrying out the same
purposes of the present invention. It should also be realized by those
skilled in the art that such equivalent constructions do not depart from
the spirit and scope of the invention as set forth in the appended
claims. The novel features which are believed to be characteristic of the
invention, both as to its organization and method of operation, together
with further objects and advantages will be better understood from the
following description when considered in connection with the accompanying
figures. It is to be expressly understood, however, that each of the
figures is provided for the purpose of illustration and description only
and is not intended as a definition of the limits of the present
invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]For a more complete understanding of the present invention,
reference is now made to the following descriptions taken in conjunction
with the accompanying drawings, in which:

[0009]FIG. 1A illustrates a side view of a circularly polarized folded
patch antenna according to an embodiment of the present invention.

[0010]FIG. 1B illustrates a top view of a circularly polarized folded
patch antenna according to an embodiment of the present invention.

[0011]FIG. 1C illustrates a plan view of a patch radiating element
according to an embodiment of the present invention.

[0012]FIG. 2A illustrates the measured axial ratio against frequency of a
prototype circularly polarized folded patch antenna built and tested
according to the embodiment illustrated by FIGS. 1A-1C.

[0013]FIG. 2B illustrates the measured return loss against frequency of a
prototype circularly polarized folded patch antenna built and tested
according to the embodiment illustrated by FIGS. 1A-1C.

[0014]FIG. 2c illustrates a right hand CP radiation pattern at the
phi=0° plane at 1.554 GHz for the embodiment of the prototype
circularly polarized folded patch antenna built and tested according to
the embodiment illustrated by FIGS. 1A-1C.

[0015]FIG. 2D illustrates a right hand CP radiation pattern at the
phi=90° plane at 1.554 GHz for the embodiment of the prototype
circularly polarized folded patch antenna built and tested according to
the embodiment illustrated by FIGS. 1A-1C.

[0016]FIG. 3A illustrates an exemplary patch geometry according to an
embodiment of the present invention, wherein asymmetry is introduced into
the top layer of the radiating element of a circularly polarized folded
patch antenna.

[0017]FIG. 3B illustrates an exemplary patch geometry according to an
embodiment of the present invention, wherein asymmetry is introduced into
the top layer of the radiating element of a circularly polarized folded
patch antenna.

[0018]FIG. 3c illustrates an exemplary patch geometry according to an
embodiment of the present invention, wherein asymmetry is introduced into
the top layer of the radiating element of a circularly polarized folded
patch antenna.

[0019]FIG. 4A illustrates an exemplary patch geometry according to an
embodiment of the present invention, wherein asymmetry is introduced into
the bottom layer of the radiating element of a circularly polarized
folded patch antenna.

[0020]FIG. 4B illustrates an exemplary patch geometry according to an
embodiment of the present invention, wherein asymmetry is introduced into
the bottom layer of the radiating element of a circularly polarized
folded patch antenna.

[0021]FIG. 5A illustrates a side view of circularly polarized folded patch
antenna according to an embodiment of the present invention, wherein
asymmetry is introduced into the radiating element by lengthening a
vertical wall portion of the radiating element.

[0022]FIG. 5B illustrates a plan view of a patch radiating element
according to an embodiment of the present invention.

[0023]FIG. 6A illustrates a side view of circularly polarized folded patch
antenna according to an embodiment of the present invention, wherein the
radiating element is folded downwards to form a radiating element with
more than two parallel layers.

[0024]FIG. 6B illustrates a plan view of a patch radiating element
according to an embodiment of the present invention.

[0025]FIG. 7A illustrates a side view of circularly polarized folded patch
antenna according to an embodiment of the present invention, wherein the
radiating element is folded upwards to form a radiating element with more
than two parallel layers.

[0026]FIG. 7B illustrates a plan view of a patch radiating element
according to an embodiment of the present invention.

[0027]FIG. 8A illustrates the perspective view of a circularly polarized
folded patch antenna according to an embodiment of the present invention
wherein the radiating element comprises a conductor on PCB material.

[0031]FIG. 8E illustrates the bottom layer of the radiating element of the
circularly polarized folded patch antenna illustrated by FIG. 8A wherein
the tails on the bottom layer are connected.

[0032]FIG. 9 illustrates an exemplary patch geometry according to an
embodiment of the present invention wherein the radiating element
includes dual feed points.

DETAILED DESCRIPTION OF THE INVENTION

[0033]FIGS. 1A and 1B illustrate a miniature circularly polarized folded
patch antenna 100 adapted according to an exemplary embodiment of the
present invention. FIG. 1A is a side view illustration of exemplary
folded patch antenna 100. Antenna 100 includes a ground plane 101, a
spacer layer 102, a radiating element 103, and a radio frequency (RF)
feed 104. As illustrated by FIG. 1A and discussed further with respect to
FIG. 1C, radiating element 103 is folded under itself to form a folded
patch.

[0034]FIG. 1B is a top view illustration of the exemplary folded patch
antenna 100. As illustrated by FIG. 1B, radiating element 103 includes a
plurality of slots, which will be discussed further with respect to FIG.
1C, and includes a RF feed point 104A. As discussed further below, the
center conductor of a coaxial cable is coupled to radiating element 103
at RF feed point 104A.

[0035]In the example of FIGS. 1A and 1B, ground plane 101 includes a
planar substrate, such as a printed circuit board, covered by metal
(e.g., copper in the example of FIGS. 1A and 1B). In the embodiment
illustrated by FIGS. 1A and 1B, the square ground plane is 0.26
λ0. Furthermore, in some embodiments, the planar substrate and
conducting material may be separated by a dielectric or by an air gap.

[0036]Spacer layer 102 is composed of a porous, light weight,
non-conductive material that consists primarily of air. In the exemplary
embodiment of FIGS. 1A and 1B, spacer layer 102 is a foam spacer, which
has a dielectric constant similar to air. In other embodiments, spacer
layer 102 can be made of, for example, glass or TEFLON®. In still
other embodiments, spacer layer 102 may be created using standoffs (e.g.,
insulator pins, dielectric spacers, etc.) to create an air gap between
ground plane 101 and radiating element 103. And in certain embodiments, a
signal line from RF feed 104 holds radiating element 103 above ground
plane 101, creating an air gap between ground plane 101 and radiating
element 103.

[0037]In the embodiment illustrated by FIGS. 1A and 1B, radiating element
103 is coupled to a transmitter or receiver by a coaxial cable which is
fed to RF feed 104. The center conductor of the coaxial cable extends
vertically up through the spacer layer 102 and is fixed to radiating
element 103 by soldering at RF feed point 104A.

[0038]According to the embodiment of the present invention illustrated by
FIGS. 1A and 1B, radiating element 103 is shaped into a folded patch. The
radiating element 103 is formed from a conducting material (copper in the
example of FIGS. 1A and 1B). In other embodiments the radiating element
may be formed from other conductors, such as aluminum, gold, or tin
plated steel. The geometry of radiating element 103 comprises a unique
configuration described with reference to FIG. 1C.

[0039]FIG. 1C shows a plan view of radiating element 103 according to the
embodiment of the invention illustrated by FIGS. 1A and 1B. As shown in
FIG. 1C, radiating element 103 is formed from a single sheet of a
conductor (e.g., copper) that can be stamped, cut, or otherwise formed to
provide the geometries disclosed herein. Radiating element 103 includes a
plurality of slots and asymmetries cut, or otherwise formed, in radiating
element 103. The slots have several purposes. For instance, the slots
lengthen the effective radiating current path of radiating element 103,
thereby allowing reduction of the radiating element's size. Also, the
slots and asymmetries introduce radiating current paths of differing
lengths, which allows excitation of two modes. The asymmetries are
designed to ensure that the current paths produce two signals of
substantially equal magnitude and 90° out of phase and are
described in more detail below.

[0040]In the embodiment illustrated by FIG. 1C, radiating element 103
includes slots 105A-105D. Each of slots 105A-105D radiates inwardly
towards the center of radiating element 103. Each of slots 105A-105D is
orthogonal to adjacent slots (i.e., the slots are at 90° angles to
neighboring slots). Slots 105A-105D define arms 106A-106D.

[0041]Each of arms 106A-106D includes a slot 107A-107D, respectively, that
defines two fingers. As shown in FIG. 1, each of arms 106A-106D is
asymmetrical--the two fingers of each arm are different lengths. This
asymmetry provides for radiation paths of different lengths within
radiating element 103. That is, the different lengths of the fingers on
allow radiating element 103 to generate and/or receive CP signals. The
lengths are selected to cause simultaneous excitation of two orthogonal
patch modes substantially equal in amplitude and 90° out of phase.

[0042]FIG. 1C illustrates the dimensions of radiating element 103 in terms
of λ0 . The dimensions of slots 105A-105D are identical.
Similarly, the dimensions of slots 107A-107D are identical. Consequently,
the dimensions of arms 106A-106D and fingers 108A-108D and 109A-109D are
identical; however, as illustrated in FIG. 3, the arms are oriented
differently. As discussed further below, with respect to FIGS. 2A-2D, the
disclosed pattern can be used to generate and receive circularly
polarized signals.

[0043]To further reduce the lateral size of radiating element 103,
radiating element 103 is designed to fold under itself. According to the
embodiment illustrated by FIG. 1C, radiating element 103 is designed to
fold along fold lines, which are shown as dashed lines on the
illustration of radiating element 103 shown in FIG. 1C. The dashed fold
lines shown in FIG. 1C are for illustration only as other embodiments may
be folded differently. In the embodiment of FIGS. 1A-1C, the radiating
element is designed to be folded down and under itself at approximately
90° angles along the fold lines. When folded along the fold lines,
radiating element 103 includes a top layer 110, bottom layer 111, and
vertical wall layers 112. In certain embodiments, radiating element 103
may be folded around a spacer element (not shown). The spacer element may
comprise, for example, a porous, light weight, non-conductive material
that consists primarily of air (e.g., foam, non-woven fabric, etc.).

[0044]As shown in FIG. 1B, the length of the radiating element for the
disclosed patch antenna is on the order of 0.15 λ0.
Miniaturization of the disclosed circularly polarized folded patch
antenna is facilitated by at least two design elements. For instance, the
introduction of slots into radiating element 103 causes radiation
patterns that effectively lengthen the radiating element. Furthermore,
the lateral size of the patch is reduced by folding radiating element 103
under itself. It should be noted that the disclosed miniaturization of
antenna 100 is facilitated without utilizing dielectric loading, in
contrast to some prior art CP patch antennas.

[0045]A prototype according to the design of the embodiment of FIGS. 1A-1C
has been built and tested. The results of testing are shown in FIGS.
2A-2D. FIG. 2A illustrates the axial ratio of circularly polarized patch
antenna 100. The antenna has an axial ratio of 1.18187 dB at 1554.265 MHz
and exhibits an axial ratio of better than 3 dB for a range of
frequencies. The antenna has a 3 dB axial ratio bandwidth of 0.26%. FIG.
2B illustrates the measured return loss of circularly polarized folded
patch antenna 100. As shown in FIG. 2B, the disclosed antenna displays
1.33% impedance bandwidth of return loss below -10 dB. The axial ratio
bandwidth is ranged inside the impedance bandwidth, which is the dotted
line in FIG. 2A. The prototype antenna demonstrated greater than 45%
efficiency and greater than 0.5 dB gain between the axial ratio
bandwidth.

[0046]FIGS. 2C and 2D illustrate actual right hand CP radiation patterns
for the embodiment of the circularly polarized patch antenna 100
illustrated and described with respect to FIGS. 1A-1C. FIG. 2c shows the
radiation pattern for folded patch antenna 100 at the Φ=0°
plane. FIG. 2D shows the radiation pattern for folded patch antenna 100
at the Φ=90° plane.

[0047]Although exemplary circularly polarized folded patch antenna 100
includes radiating element 103 of the geometry illustrated in FIG. 1C,
folded patch antennas according to the present invention may include
radiating elements of any geometry that excites two different orthogonal
modes 90° out of phase and substantially equal in magnitude. FIGS.
3A-3C and 4A-4B illustrate exemplary patch geometries for use in
embodiments of the present invention.

[0048]FIGS. 3A-3C illustrate embodiments of the present invention where
asymmetries are introduced to the top layer of a folded radiating
element. FIGS. 3A-3C do not show the vertical wall layers or bottom
layers of the folded patch. The disclosed geometries are examples of the
top layer of a radiating element of a circularly polarized folded patch
antenna according to embodiments of the present invention.

[0049]A folded patch radiating element with a top layer according to the
geometry illustrated by FIG. 3A has been shown to generate and receive
circularly polarized signals. Top layer 300 includes a plurality of
symmetrical slots 301A-301D on each side of the top layer. These slots
effectively lengthen the radiating element by creating a meandering path.
Top layer 300 also includes a first slot pair (slots 302A and 302C) and a
second slot pair (slots 303B and 303D). As illustrated by FIG. 3A, the
prongs of the first slot pair and second slot pair are of different
lengths. The lengths of the slot prongs are selected to ensure that
radiating element 300 excites two orthogonal modes 90° out of
phase and substantially equal in magnitude.

[0050]FIG. 3B illustrates another top layer geometry capable of exciting
two modes substantially equal in magnitude and 90° out of phase.
Top layer 310 includes a plurality of symmetrical slots 311A-311D on each
side of the top layer. Slots 311A-311D effectively lengthen the radiating
element by creating longer paths. In the example of FIG. 3B, radiating
circuits of different lengths are created based on the differences in the
sizes of slots 312A-312D. Slots 312A-312D radiate inwards and terminate
in circular areas. The circular area at the end of slots 312A and 312C
has a larger area than the circular area at the ends of slots 312B and
312D. In this example, the size of the circular areas is selected to
ensure that the radiating element 310 excites two orthogonal modes
90° out of phase.

[0051]FIG. 3c also illustrates a top layer geometry capable of exciting
two modes substantially equal in magnitude and 90° out of phase.
Top layer 320 includes a plurality of symmetrical slots 321A-321D on each
side of the top layer. Slots 321A-321D effectively lengthens the
radiating element by creating a meandering path. In the example of FIG.
3C, slots 322A-322D radiate inwards and turn outwards at approximately
45° and then inwards at approximately 90° to form a
pinwheel-like pattern. The asymmetry in direction of the patches is
selected to ensure that the radiating element excites two orthogonal
modes 90° out of phase.

[0052]FIGS. 4A and 4B illustrate plan views of radiating elements
according to embodiments of the present invention. Radiating elements 400
and 410 are designed to be folded along the illustrated fold lines to
form a folded patch with a top layer (top layers 401 and 411), a vertical
wall layer (vertical wall layers 402 and 412), and a bottom layer
comprising four arms (bottom layer 403 and 413). As illustrated by FIGS.
4A and 4B, the top layers of radiating elements 400 and 410 are
symmetrical. In these examples, the asymmetries that drive two orthogonal
modes 90° out of phase are introduced in the bottom layers (403
and 413) of the folded patch radiating elements 400 and 410.

[0053]In the example of FIG. 4A, the asymmetry that facilitates circular
polarization in radiating element 400 is introduced in each arm of bottom
layer 403. Fingers 404A-404D and 405A-405D are defined by slots
406A-406D. As shown by FIG. 4A, fingers 404A-404D are longer than fingers
405A-405D. The lengths of the fingers are selected to cause radiating
element 400 to excite two orthogonal modes 90° out of phase and
substantially equal in magnitude.

[0054]In the example of FIG. 4B, the asymmetry that facilitates circular
polarization in radiating element 410 is introduced in each arm of bottom
layer 413. As shown by FIG. 4B, tails 414A-414D are longer than tails
415A-415D. The lengths of the tails are selected to cause radiating
element 400 to excite two orthogonal modes 90° out of phase and
substantially equal in magnitude.

[0055]FIGS. 5A and 5B illustrate a circularly polarized folded patch
antenna according to an embodiment of the present invention where the
asymmetries are introduced using unequal wall heights. As shown in FIG.
5A, circularly polarized folded patch antenna 500 includes a ground plane
501, spacer layer 502, radiating element 503, and feed element 504.
Radiating element 500 includes vertical walls 505A and 505B of different
heights. The differences in vertical wall height create radiation
circuits of different lengths and are selected to excite two orthogonal
modes 90° out of phase.

[0056]FIG. 5B illustrates a plan view of radiating element 503. Radiating
element 503 includes slots 506A-506D that defines arms 507A-507D. Each of
arms 507A-507D includes two fingers of different lengths defined by slots
508A-508D. As shown in FIG. 5B, the dashed fold lines define vertical
walls of unequal height. When radiating element 503 is folded under
itself along the fold lines, walls 505A and 505B are formed with
differing heights.

[0057]Turning now to FIGS. 6A-6B and 7A-7B, embodiments of the present
invention are illustrated wherein radiating patch elements are folded
multiple times to provide a plurality of horizontal layers. By increasing
the number of folds, the lateral dimensions of a patch may be further
reduced, allowing for more compact packaging of the folded patch antenna.
Although FIGS. 6A-6B and 7A-7B present embodiments with three horizontal
layers and two vertical wall layers, various embodiments of the present
invention do not limit the number of times a patch radiating element may
be folded.

[0058]FIG. 6A illustrates a circularly polarized folded patch antenna 600
according to one embodiment of the present invention. The embodiment
shown in FIG. 6A comprises a ground plane 601, a spacer layer 602, a
radiating element (patch) 603, and a feed element 604. As shown in FIG.
6A, radiating element 603 is folded to include three horizontal layers (a
top layer 605, a middle layer 606, a bottom layer 607) and two vertical
wall layers (first vertical wall layer 608 and second vertical wall layer
609). In this embodiment, the feed element is fed upward through space in
radiating element 603 to top layer 605. FIG. 6B illustrates a plan view
for radiating element 603. As shown by the dashed fold lines, radiating
element 603 is designed to be folded downwards as shown in FIG. 6A.

[0059]FIG. 7A illustrates a circularly polarized folded patch antenna 700
according to an embodiment of the present invention. The embodiment shown
in FIG. 7A comprises a ground plane 701, a spacer layer 702, a radiating
element (patch) 703, and a feed element 704. As shown in FIG. 7A,
radiating element 703 is folded to include three horizontal layers (a top
layer 705, a middle layer 706, a bottom layer 707) and two vertical wall
layers (first vertical wall layer 708 and second vertical wall layer
709). In this embodiment, feed element 704 is not fed through the
radiating element as with the embodiment illustrated by FIG. 6A; rather,
the feed element is fed directly to top layer 705. Thus, as illustrated
by FIG. 6A and FIG. 7A, radiating elements according to the present
invention may be folded upward or downward. FIG. 7B illustrates a plan
view for radiating element 703. As shown by the dashed fold lines,
radiating element 703 is designed to be folded upwards as shown in FIG.
7A.

[0060]Embodiments of the present invention are not limited to radiating
elements comprised of a single conducting element. According to
embodiments of the present invention the radiating element may comprise a
conductor on printed circuit board (PCB) material. In other embodiments
the radiating element may comprise a plurality of conducting layers
connected by conducting connectors or pins.

[0061]FIGS. 8A-8E illustrate a miniature circularly polarized patch
antenna adapted according to an embodiment of the present invention
wherein the radiating element includes conductors printed on PCB
material. As illustrated in FIG. 8A, the radiating element of a
circularly polarized folded patch antenna according to embodiments of the
present invention can be fabricated using PCB material. The circularly
polarized folded patch antenna 800 includes a ground layer 801, a spacer
layer 802 (more clearly shown in FIG. 8B), a radiating element 803, and a
feed element 804. In the embodiment illustrated by FIG. 8A, radiating
element 803 includes a top layer 805, a bottom layer 806, and conducting
pins 807.

[0062]As more clearly illustrated by FIG. 8c, top layer 805 includes an
antenna pattern etched onto PCB. In the embodiment illustrated by FIGS.
8A-8D, the asymmetry in radiating element 803 is introduced in top layer
805 of radiating element 803. As shown in FIG. 8c, asymmetry is
introduced at elements 808A-808D etched into top layer 805. The slots
defining elements 808B and 808D are smaller than the slots defining 808A
and 808C. Elements 808A-808D are selected to excite two orthogonal modes
90° out of phase and of substantially equal magnitude.

[0063]FIG. 8D illustrates bottom layer 806 according to the embodiment
illustrated by FIGS. 8A-8D. As shown in FIG. 8D, each of arms 809A-809D
is symmetrical in this embodiment. The radiation paths of bottom layer
806 are connected to the radiation paths of top layer 805 by conducting
pins 807. In certain embodiments, as illustrated by FIG. 8E, portions of
the radiation paths may be connected to alter, or tune, the radiation
element. In the example of FIG. 8, tails 808A and 808C are connected at
soldering points 809A and 809B and tails 808B and 808D are connected at
soldering points 810A and 810B thereby tuning the response of the
radiating element shown in FIGS. 8A-8E.

[0064]As illustrated in FIG. 9, embodiments of the present invention may
include two orthogonal feeds. In the embodiment illustrated by FIG. 9,
radiating element 900 includes dual feed points 901A and 901B, and
radiating element 900 is fed two signals, one at feed point 901A and the
second at feed point 901B. In embodiments utilizing a dual feed, the
radiating element's geometry can be both symmetric and asymmetric. Dual
feed embodiments of the present invention exhibit wider axial ratio and
impedance bandwidth when fed with signals substantially equal in
magnitude but 90° out of phase.

[0065]Various embodiments of the invention provide advantages over prior
art antenna systems. For instance, various disclosed folded patch
antennas are smaller than other air substrate CP antennas. Furthermore,
various disclosed folded patch antennas do not require expensive
dielectrics to facilitate miniaturization. Moreover, various disclosed
miniature folded patch antennas have simple antenna structures that can
be quickly and inexpensively manufactured. Although the embodiments of
the present invention may be used in any number of applications, the
circularly polarized folded patch antenna disclosed herein may find
particular use in GPS units, satellite televisions, RFID base stations,
satellite communications, cellular telephones, or other mobile
communication devices.

[0066]Although the present invention and its advantages have been
described in detail, it should be understood that various changes,
substitutions and alterations can be made herein without departing from
the spirit and scope of the invention as defined by the appended claims.
Moreover, the scope of the present application is not intended to be
limited to the particular embodiments of the process, machine,
manufacture, composition of matter, means, methods and steps described in
the specification. As one of ordinary skill in the art will readily
appreciate from the disclosure of the present invention, processes,
machines, manufacture, compositions of matter, means, methods, or steps,
presently existing or later to be developed that perform substantially
the same function or achieve substantially the same result as the
corresponding embodiments described herein may be utilized according to
the present invention. Accordingly, the appended claims are intended to
include within their scope such processes, machines, manufacture,
compositions of matter, means, methods, or steps.